This application claims priority to Korean Patent Application No. 2003-0069143, filed on Oct. 6, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates generally to IC (integrated circuit) fabrication, and more particularly to a method and system for planarizing IC material such as an insulating layer using a plurality of slurries.
2. Description of the Related Art
An integrated circuit (IC) is fabricated onto a semiconductor substrate such as a silicon substrate. Various materials such as insulating layers are formed onto the semiconductor substrate for fabricating the IC. The surface of the insulating layer needs to be formed into specialized patterns for fabricating the IC. Polishing is widely used to planarize the surface of the insulating layer. In particular, chemical mechanical polishing (CMP) is commonly used to planarize an insulating layer having steps formed in the upper surface thereof.
In a conventional CMP process, a polishing speed and a degree of planarization varies depending on the type and density of patterns of films that are polished. More particularly, if the heights of steps formed in the upper surface of an oxide film are greater than a predetermined height, the surface may not be sufficiently planarized when the CMP process is completed. Such incomplete planarization poses problems in subsequent fabrication processes, especially for subsequent photolithography.
To prevent such problems, a high planarity slurry, in particular, a ceria based slurry is widely used. If integrated circuit structure(s) below an oxide layer have a non-planar profile, the upper surface of the oxide layer is formed with steps. Such non-planarity is especially common within a cell array region of a memory device fabricated on the silicon substrate. In that case, the removal rate of the oxide layer during polishing is decreased because the CMP process is performed on an uneven surface of the oxide layer. Therefore, a long time is required to complete the CMP process using the high planarity slurry. Moreover, sufficient planarization of the oxide layer may not be attainable even if a high planarity slurry is used.